The objective of this proposal is to establish a quantitative immunoassay for gp48. The clinical significance of this gp48 immunoassay will then be assessed by monitoring patients undergoing therapy and detecting patients with malignant lesions of epithelial origin. To achieve this, we propose to biosynthetically label gp48 with 3H-or 14C-carbohydrate precursors using any of the systems available to us, with the main emphasis on using human breast cancer surgical specimens maintained in organ culture. In addition, we will examine human breast tumor lines propagated in athymic nude mice and cell culture systems of established malignant human breast epithelial cell lines as potential sources for labelled gp48. The biosynthetically labelled gp48 will be used as a tracer to isolate mg quantities of this component from either of these three systems or from the sera of patients with demonstrated elevation of glycoproteins in the alpha2-beta electrophoretic region. Purification procedures will utilize, in addition to the standard biochemical steps, lectin affinity chromatography, preparative electrophoresis, immunoaffinity chromatography and ion-exchange chromatography. The purified glycoprotein will be used for the production of immune antisera. After appropriate adsorptions, the specific antisera will be used to establish a quantitative immunoassay using a nonradioactive immunodiagnostic procedure with rate nephelometry instrumentation, or radioimmunoassay using 125I-labelled gp48.